Characterization of cellulolytic activity from digestive fluids of Dissosteira carolina (Orthoptera: Acrididae).

ABSTRACT

Previous screening of head-derived and gut fluid extracts of Carolina grasshoppers, Dissosteira carolina (L.) revealed relatively high activity against cellulase substrates when compared to other insect groups. In this work we report on the characterization and identification of enzymes involved in cellulolytic activity in digestive fluids of D. carolina. In zymograms using carboxymethylcellulose (CMC) as substrate, we detected four distinct cellulolytic protein bands in D. carolina gut fluids, common to all developmental stages. These cellulolytic enzymes were localized to foregut and midgut regions of the D. carolina digestive tract. Cellulases were purified from D. carolina head and gut fluid extracts by liquid chromatography to obtain N-terminal amino acid sequence tags. Database searches with sequence tags from head fluids indicated high similarity with invertebrate, bacterial and plant beta1,4-endoglucanases, while no homologues were identified for the gut-derived protein. Our data demonstrate the presence of cellulolytic activity in the digestive system of D. carolina and suggest that cellulases of endogenous origin are present in this organism. Considering that this grasshopper species is a pest of grasses, including switchgrass that has been suggested bioethanol feedstock, characterization of insect cellulolytic systems may aid in developing applications for plant biomass biodegradation for biofuel production.